CN112097680B - Surface topography testing device and testing method based on multi-cavity FP interferometer - Google Patents

Surface topography testing device and testing method based on multi-cavity FP interferometer Download PDF

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CN112097680B
CN112097680B CN202010969430.XA CN202010969430A CN112097680B CN 112097680 B CN112097680 B CN 112097680B CN 202010969430 A CN202010969430 A CN 202010969430A CN 112097680 B CN112097680 B CN 112097680B
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fiber end
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时金辉
俞立本
光东
吴许强
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Anhui University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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    • G01B9/02—Interferometers

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Abstract

The invention discloses a surface topography test device and a test method based on a multi-cavity FP interferometer, the device comprises a laser, an optical fiber beam splitter, an optical circulator group, an optical fiber end surface array, a reflecting surface to be tested and a photoelectric detector, laser emitted by the laser is divided into a plurality of beams by the optical fiber beam splitter, the beams are transmitted to the optical fiber array through the optical circulator, the beams are emitted from the optical fiber end surface in the optical fiber end surface array and vertically irradiate on the reflecting surface to be tested and are reflected back to the optical fiber, the reflected light interferes with the reflected light of the optical fiber end surface, the interference light is transmitted to the photoelectric detector and is converted into electric signals, the phase difference of each interference light is compared, the cavity length difference of each FP interference cavity is calculated through the phase difference, and the height position of each irradiating surface on the reflecting surface to be tested is calculated according to the known axial dislocation relation between the optical fiber end surfaces in the optical fiber array. The invention can simultaneously test the appearance of the surface to be tested, and avoids the time required by scanning and the mechanical vibration interference caused by scanning without the scanning process.

Description

Surface topography testing device and testing method based on multi-cavity FP interferometer
Technical Field
The invention relates to a device and a method for measuring optical sensing information, in particular to a surface topography testing device and a surface topography testing method based on a multi-cavity FP interferometer.
Background
The development of the society needs to acquire external information in a multi-level and high-depth manner, and various sensors are the main modes for acquiring the external information. Optical sensing, particularly interferometric optical sensing, is gaining attention for its high sensitivity, electromagnetic interference resistance, and broad applicability. Meanwhile, the performance requirements of electronic products and high-precision optical mirrors are higher and higher, which puts higher demands on the quality of the raw material, i.e., wafer, of the semiconductor integrated circuit. The warping degree of the wafer directly affects the yield of the processes such as photoetching, wafer bonding and the like in subsequent production. At present, the measurement method for wafer warpage is generally divided into an electron microscope method, an optical interference method and a mechanical probe method.
The electron microscope method uses a scanning electron microscope as a means to detect the surface morphology state. The method has extremely high measurement precision, but the device is high in price, and has high requirements on the measurement environment. The optical interference method integrates optics and electronics, and has the defects of small dynamic measurement range, poor universality, high manufacturing cost of the device and the like. The mechanical probe method is represented by an atomic force microscope, and the principle of the mechanical probe method is that van der waals force between atoms is utilized to present the surface characteristics of a measured sample, and through a point-by-point measurement and data fitting mode, the measurement efficiency is low, and the surface of a measured wafer can be scratched.
Therefore, how to make up for the defects of the above method, and at the same time, meet the requirements of high precision and low cost, improve the measurement efficiency, enlarge the measurement dynamic range, and reduce the requirements of the measurement on the environment is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a surface morphology testing device and a surface morphology testing method based on a multi-cavity FP interferometer, so that the cost of realizing a sensing device can be reduced, and the sensitivity and the stability of a sensing system can be improved.
The purpose of the invention can be realized by the following technical scheme:
a surface topography testing device based on a multi-cavity FP interferometer comprises a laser, an optical fiber beam splitter, an optical circulator group, an optical fiber end surface array, a reflecting surface to be tested and a photoelectric detector group;
the working method of the appearance testing device comprises the following steps:
laser emitted by the laser is divided into a plurality of light beams through the optical fiber beam splitter, the light beams are transmitted to the optical fiber end face array through the optical ring set, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on the reflecting surface to be detected and then are reflected back to the optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and the irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to the photoelectric detector through the optical ring set and is converted into an electric signal.
As a further aspect of the invention, the laser is a single wavelength narrow linewidth laser.
As a further scheme of the invention, the optical fiber end face array is formed by parallel multiple optical fibers, the optical fiber end faces are distributed in an array manner, and dislocation is formed along the axial direction of the optical fibers in a rated length.
As a further aspect of the invention, nominal length means that the length of the offset between each end face is a known amount.
As a further scheme of the invention, the end face of the optical fiber and an intracavity medium of the FP interference cavity form refractive index difference to realize reflection of light beams, and the end face of the optical fiber is a plane which is directly cut out and is vertical to the axial direction of the optical fiber or is coated with a film layer on the end face of the optical fiber.
As a further scheme of the present invention, the optical fiber end surface array has k optical fiber end surfaces, and k irradiation area surfaces are formed on the reflection surface to be measured to form k FP interference cavities, where k =2,3.
As a further scheme of the invention, the surface topography testing method of the surface topography testing device based on the multi-cavity FP interferometer comprises the following steps:
laser emitted by a laser is divided into a plurality of light beams through an optical fiber beam splitter, the light beams are transmitted to an optical fiber end face array through an optical ring set, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on a reflecting surface to be detected and then are reflected back to an optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and an irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to a photoelectric detector through the optical ring set and is converted into an electric signal;
and calculating the phase difference of each interference light, calculating the cavity length difference of each FP interference cavity through the phase difference, and calculating the height position of each irradiation area surface on the reflecting surface to be measured according to the known axial dislocation relation between the end surfaces of the optical fibers in the optical fiber array.
As a further scheme of the invention, the specific method for calculating the phase difference of each interference light, calculating the cavity length difference of each FP interference cavity through the phase difference and calculating the height position of each irradiation area surface on the reflecting surface to be measured according to the known axial dislocation relation between the end surfaces of the optical fibers in the optical fiber array comprises the following steps:
the output signals of the interferometers are as follows:
Figure BDA0002683555880000031
wherein j =1,2,3 j Is a direct current component of an interference signal, B j Is the alternating current component of the interference signal,
Figure BDA0002683555880000034
is the phase difference of two beams in the interference cavity, lambda is the output light wavelength of the laser, n is the refractive index of the medium in the cavity,
Figure BDA0002683555880000032
is the phase difference between two interference cavities, L 0 Setting the axial cavity length difference of any two FP cavities as 0 because the axial dislocation quantity of the end face of the optical fiber along the optical fiber is rated, namely the cavity length difference is the height position difference of each irradiation area surface on the reflecting surface to be measured;
obtaining the phase difference between two interference cavities by phase demodulation or white light interference
Figure BDA0002683555880000033
From the above equation, the following equation can be derived:
Figure BDA0002683555880000041
the cavity length difference of the two interference cavities, namely the height difference of the two irradiation area surfaces can be obtained; and setting the irradiation area surface of a certain interference cavity as a reference surface, and respectively calculating the height difference between the irradiation area surface and other irradiation area surfaces to obtain the shape state of the reflecting surface to be measured.
The invention has the beneficial effects that:
1. according to the surface topography testing device and the testing method based on the multi-cavity FP interferometer, provided by the invention, the topography parameters are simultaneously measured at one time, and the scanning time required by the scanning type detecting device and the change of a detecting point caused by the scanning time interval are avoided.
2. According to the surface topography testing device and method based on the multi-cavity FP interferometer, provided by the invention, the topography parameters are simultaneously measured at one time, and the interference of a scanning type detection device caused by the mechanical displacement of a scanning device is avoided.
3. The invention adopts non-contact measurement to ensure that the surface of the surface to be measured is not damaged.
Drawings
The invention is described in further detail below with reference to the figures and the specific embodiments.
FIG. 1 is a schematic structural diagram of a surface topography test device based on a multi-cavity FP interferometer of the present invention.
Fig. 2 is a diagram of a fiber end array architecture of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1 to 2, the embodiment discloses a surface topography testing device and a testing method based on a multi-cavity FP interferometer, the device includes a laser, an optical fiber beam splitter, an optical ring set, an optical fiber end surface array, a reflective surface to be tested, and a photoelectric detector set;
the working method of the surface topography testing device based on the multi-cavity FP interferometer comprises the following steps:
laser emitted by a laser is divided into a plurality of light beams through an optical fiber beam splitter, the light beams are transmitted to an optical fiber end face array through an optical ring set, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on a reflecting surface to be detected and then are reflected back to an optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and an irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to a photoelectric detector through the optical ring set and is converted into an electric signal;
example 2
The embodiment discloses a preparation scheme of the surface topography testing device based on the multi-cavity FP interferometer, which comprises the following steps:
setting the axial dislocation length of the end face of the optical fiber to be 0; a plurality of optical fibers are fixed on a plane substrate in parallel, and the end faces of the optical fibers and the plane substrate are in the same horizontal plane through end face grinding.
And vertically aligning the successfully manufactured optical fiber end surface array to the area to be measured of the reflecting surface to be measured along the light beam direction to form a plurality of FP (Fabry-Perot) cavities.
Example 3
A surface topography test method of a surface topography test device based on a multi-cavity FP interferometer comprises the following steps:
laser emitted by a laser is divided into a plurality of light beams through an optical fiber beam splitter, the light beams are transmitted to an optical fiber end face array through an optical ring set, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on a reflecting surface to be detected and then are reflected back to an optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and an irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to a photoelectric detector through the optical ring set and is converted into an electric signal;
and comparing the phase difference of each interference light, calculating the cavity length difference of each FP interference cavity through the phase difference, and calculating the height position of each irradiation area surface on the reflecting surface to be measured according to the known axial dislocation relation between the end surfaces of the optical fibers in the optical fiber array.
Specifically, the change of the FP cavity length is analyzed and calculated by adopting a phase demodulation algorithm on an electric signal converted from the interference light beam;
the output signals of the interferometers are as follows:
Figure BDA0002683555880000061
wherein j =1,2,3 j Is a direct current component of an interference signal, B j Is the alternating current component of the interference signal,
Figure BDA0002683555880000065
is the phase difference between two beams in the interference cavity, and lambda is the laserN is the refractive index of the medium within the cavity,
Figure BDA0002683555880000062
is the phase difference between two interference cavities, L 0 The axial cavity length difference of any two FP cavities is set to be 0 at present due to the rated axial dislocation quantity of the optical fiber end surface along the optical fiber, namely the cavity length difference is the height position difference of each irradiation area surface on the reflecting surface to be measured.
Obtaining the phase difference between two interference cavities by phase demodulation or white light interference
Figure BDA0002683555880000063
From the above formula, the following formula can be obtained
Figure BDA0002683555880000064
The cavity length difference of the two interference cavities, namely the height difference of the two irradiation area surfaces can be obtained by the formula; and setting the irradiation area surface of a certain interference cavity as a reference surface, and respectively calculating the height difference between the irradiation area surface and other irradiation area surfaces to obtain the shape state of the reflecting surface to be measured.
The foregoing is merely exemplary and illustrative of the present invention and various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the scope of the invention as defined in the following claims.

Claims (4)

1. A surface appearance testing device based on a multi-cavity FP interferometer is characterized by comprising a laser, an optical fiber beam splitter, an optical ring group, an optical fiber end surface array, a reflecting surface to be tested and a photoelectric detector group;
the working method of the appearance testing device comprises the following steps:
laser emitted by a laser is divided into a plurality of light beams through an optical fiber beam splitter, the light beams are transmitted to an optical fiber end face array through an optical ring group, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on a reflecting surface to be detected and then are reflected back to the optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and an irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to a photoelectric detector through the optical ring group and is converted into an electric signal;
the optical fiber end face arrays are formed by parallel optical fibers, the optical fiber end faces are distributed in an array manner, and dislocation is formed along the axial direction of the optical fibers in a rated length;
the method comprises the following steps that k optical fiber end faces are arrayed on an optical fiber end face, k irradiation area faces are formed on a reflecting face to be measured, and k FP interference cavities are formed, wherein k =2,3.;
the testing method of the surface topography testing device comprises the following steps:
laser emitted by a laser is divided into a plurality of light beams through an optical fiber beam splitter, the light beams are transmitted to an optical fiber end face array through an optical ring set, the light beams are emitted from the optical fiber end face in the optical fiber end face array and vertically irradiate on a reflecting surface to be detected and then are reflected back to an optical fiber, the reflected light interferes with the reflected light of the optical fiber end face, an FP interference cavity is formed by the optical fiber end face and an irradiation area surface on the corresponding reflecting surface to be detected, and the interference light is transmitted to a photoelectric detector through the optical ring set and is converted into an electric signal;
calculating the phase difference of each interference light, calculating the cavity length difference of each FP interference cavity through the phase difference, and calculating the height position of each irradiation area surface on the reflecting surface to be measured according to the known axial dislocation relation between the optical fiber end surfaces in the optical fiber array;
the specific method for calculating the phase difference of each interference light, calculating the cavity length difference of each FP interference cavity through the phase difference and calculating the height position of each irradiation area surface on the reflecting surface to be measured according to the axial dislocation relation between the end surfaces of the optical fibers in the known optical fiber array comprises the following steps:
the output signals of the interferometers are as follows:
Figure FDF0000019372570000021
wherein j =1,2,3 j Is a direct current component of an interference signal, B j Is the alternating current component of the interference signal,
Figure FDF0000019372570000022
is the phase difference of two beams in the interference cavity, lambda is the output light wavelength of the laser, n is the refractive index of the medium in the cavity,
Figure FDF0000019372570000023
is the phase difference between two interference cavities, L 0 Setting the axial dislocation quantity of the optical fiber end face along the optical fiber to be rated as 0 for any two FP cavity axial cavity length differences, namely, the cavity length difference is the height position difference of each irradiation area surface on the reflecting surface to be measured;
obtaining the phase difference between two interference cavities by phase demodulation or white light interference
Figure FDF0000019372570000025
From the above equation, the following equation can be derived:
Figure FDF0000019372570000024
obtaining the cavity length difference of the two interference cavities according to the previous formula, namely the height difference of the two irradiation area surfaces; and setting the irradiation area surface of a certain interference cavity as a reference surface, and respectively calculating the height difference between the irradiation area surface and other irradiation area surfaces to obtain the shape state of the reflecting surface to be measured.
2. The multi-cavity FP interferometer-based surface topography test device according to claim 1, wherein said laser is a single wavelength narrow linewidth laser.
3. The apparatus of claim 2, wherein the nominal length is a known offset length between each end face.
4. The surface topography testing device based on the multi-cavity FP interferometer according to claim 3, wherein the reflection of the light beam is realized by the refractive index difference formed between the end face of the optical fiber and the intracavity medium of the FP interference cavity, and the end face of the optical fiber is a plane which is directly cut out and is perpendicular to the axial direction of the optical fiber or is coated with a film layer.
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